摘要
采用热分析法研究了Al2O3、Fe2O3和MnCO3作为添加剂对CaO固硫反应过程的影响,用等效粒子模型对固硫反应过程进行表征,求得了其固硫反应动力学参数.结果表明:MnCO3与Fe2O3对CaO固硫反应的作用机理相同,能提高固硫反应速率常数、产物层有效扩散系数和钙的转化率.通过计算等动力学温度、活化能大小可以判断添加剂对固硫反应活性影响的趋势,但不能准确衡量添加剂对固硫反应活性的贡献;对应温度下的反应速率常数和产物层有效扩散系数更能准确反映添加剂对固硫反应的影响大小.非化学计量金属氧化物通过高温下氧离子、金属离子较强的扩散特性来催化固硫表面化学反应和促进产物层扩散反应.根据不同添加剂的作用机理和对固硫反应的不同控制阶段的影响规律,针对添加剂发挥作用的温度特性和化学反应计量关系复合掺入添加剂,可进一步提高固硫剂转化率.
The additive effects of Al2O3, Fe2O3 and MnCO3 on CaO sulfation kinetics were investigated by thermogravimetic analysis method and modified grain model. The activation energy （Ea） and the pre-exponential factor （k0） of surface reaction, the activation energy （Ev） and the pre-exponential factor （Do） of product layer diffusion reaction were calculated according to the model. Additions of MnCO3 can enhance the initial reaction rate, product layer diffusion and the final CaO conversion of sorbents, the effect mechanism of which is similar to that of Fe2O. The method based isokinetic temperature T8 and activation energy can not estimate the contribution of additive to the sulfation reactivity, the rate constant of the surface reaction （k）, and the effective diffusivity of reactant in the product layer （Ds） under certain experimental conditions can reflect the effect of additives on the activation. Unstoichiometric metal oxide may catalyze the surface reaction and promote the diffusivity of reactant in the product layer by the crystal defect and distinct diffusion of cation and anion. According to the mechanism and effect of additive on the sulfation, the effective temperature and the stoichiometric relation of reaction, it is possible to improve the utilization of sorbent by compounding more additives to the calcium-based sorbent.
出处
《环境科学》
EI
CAS
CSCD
北大核心
2006年第2期219-223,共5页
Environmental Science
基金
国家自然科学基金项目(59976019)
山东省自然科学基金项目(Y2003F07)
关键词
添加剂
CaO固硫反应
动力学
additive
CaO
desulfurization reaction
kinetics
